Set unacknowledged mode= of radio link control on RM502 modem

IoT Modules 5G Module
1

Does anyone know how to set unacknowledged mode (UM) of radio link control on RM502 modem?

Thanks,
FC

2

Dear Sir,
RM502Q support this feature. it is the radio link control protocol between the module and base station,thanks!

3

Peter

Which AT command I need to use to enable unacknowleged mode?

Thanks,
FC

4

Enable by default, no at command to control.

5

OK. What command to use if I want to change to acknowledged mode or transparent mode?

FC

6

hi,FC_Jeng:
According to different service types, different SDU (service data unit) will be generated and corresponding PDUs (protocol data unit) will be generated at the RLC layer, which are defined by 3GPP protocol specifications. For example, VoIP or video (high real-time service) adopts UM mode at the RLC layer, and FTP or WEB adopts AM mode at the RLC layer.
You are unable to specify a certain mode by AT command.

7

My application is to send data in UDP mode from my PC to AWS server.
How do I know which service type of my application uses?
Is there a way to enable my application in high real-time service type?

Thanks,
FC

8

If you are sure that you need to confirm the corresponding RLC layer transport mode, you can grab the Log and confirm it by means of signaling parsing.

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9

Which tool do you use to grab the log?
I have 2 questions regarding UM mode:

  1. Which SW decides to use UM mode? Is the modem FW making a decision on this?
  2. If yes, what is the criteria to use to decide which mode to use?

Thanks,

10

hi,FC_Jeng:
tool:https://quectel123-my.sharepoint.cn/:u:/g/personal/ae-fae_dom_quectel_com_cn/EW-Ip6jxQWpGm9OKiHBN1Z4BbMZUC8VjmYbnqHyjQc65wg?e=oDe6uM
manual:https://quectel123-my.sharepoint.cn/:w:/g/personal/ae-fae_dom_quectel_com_cn/EVqausq20mhKqkGwgXnIV9QB1OGU9-BPKjMac6Ms1DlaZw?e=p2zIgl
36322-g00.pdf (1.1 MB)

11

Thanks for the tool and doc.
Two questions:

  1. Do I need to do “Connect the USB port (Take EC20 as an example) of the module to the Windows via jump wire” on the RM502? I have a USB connector on module adapter.
  2. Can you answer my questions in previous message below:
    1. Which SW decides to use UM mode? Is the modem FW making a decision on this?
    2. If yes, what is the criteria to use to decide which mode to use?
12

hi,FC_Jeng:
1、yes,you can;
2、The RLC layer transmission mode is not determined by SW or HW, but mainly by services；The data of the SERVICES or APPLICATION layer is encapsulated into the corresponding SDU, and then transferred to the RLC layer and mapped into the corresponding PDU(using the corresponding UM or AM transmission mode).

13

Herbert

Do you have an example how to map my application to SDU and PDU uses UM mode for data transfer?

My application is a UDP application which sends data at a regular interval via RM502 which shows as a network adapter in ubuntu system

FC

14

hi,FC_Jeng:
If the module transmits data for HD video phone, the RLC layer transmission mode should be UM.
I would like to know what your purpose is for configuring RLC layer transport mode (UM or AM);
On the user plane, RLC layer belongs to L2,TCP or UDP layer belongs to L3.There is no direct correlation between them.

15

Herbert

Our application requires very low latency. My understanding is AM latency is higher than UM. This is the reason our app needs to use UM.

In fact, our application is video transmission and we are sending dummy data or test purpose currently.

How does RLC know the data is video?

Thanks,
FC

16

hi,FC_Jeng:
If the module transmits high real-time video, the module can independently establish high real-time service with the network and provide dedicated bearer, without you manually configuring the transmission mode.

17

Do you have a document to describe how to establish a dedicated bearer for a realtime video service?

Thanks,

18

hi,FC_Jeng:
There is no relevant document, but you do not need to worry, the bearer is decided by the network through self-negotiation, you do not need to make the corresponding configuration according to different services.

19

Is log capture utility available on Linux?
What information does the log have?
I am looking for packet retranmission events, mac_retx and rlc_retx` (See the link below) to analyze retransmission latency:

Fine-grained Latency Analyzers — MobileInsight Official Website

FC